[System UX VD] [BB] Define Building blocks for loading process components
Merge pull request #8049 from asutherland/email-progress-candybar-on-timeout

Bug 834653 - [EMAIL] Message list synchronization progress bar should become indeterminate/show "candybar" state after a timeout since last progress bar update. r=squib(cherry picked from commit 83d98dc9b6fd0322bf5ec79f9dcc5269e6034f1a)
Merge pull request #8093 from asutherland/email-progress-candybar-v1-train

Bug 834653 - [EMAIL] Message list synchronization progress bar should become indeterminate/show "candybar" state after a timeout since last progress bar update. v1-train landing. a=akeybl for v1-train landing.